[PATCH] optimized SPU specific code for str[n]cpy and str[n]cat
Jeff Johnston
jjohnstn@redhat.com
Tue Feb 12 21:42:00 GMT 2008
Sorry Patrick. straddr.h was added, but strcpy.h wasn't. It was not
marked as "new" so I didn't specifically keep an eye out for it when I
did the check-in.
Should be fine now.
-- Jeff J.
Patrick Mansfield wrote:
> On Mon, Feb 11, 2008 at 05:20:21PM -0500, Jeff Johnston wrote:
>> Patch applied.
>>
>> -- Jeff J.
>
> Thanks, can you check the header files?
>
> The files straddr.h and strcpy.h do not seem to have made it into cvs.
>
> Let me know if you would like another patch.
>
> -- Patrick Mansfield
>
>> Patrick Mansfield wrote:
>>> Jeff - can you please apply?
>>>
>>> Optimized SPU specific code for str[n]cpy and str[n]cat.
>>>
>>> These decrease (for simple performance tests) execution times compared to
>>> current SPU code for these functions by 20 to 50 percent.
>>>
>>> Generally, code size increases, with a worst case increase of 680 bytes.
>>>
>>> newlib/ChangeLog:
>>>
>>> 2008-02-11 Patrick Mansfield <patmans@us.ibm.com>
>>>
>>> * libc/machine/spu/straddr.h: New file, supplies _straddr.
>>> * libc/machine/spu/strcat.c: Use _straddr and _strcpy.
>>> * libc/machine/spu/strcpy.c: Use _strcpy.
>>> * libc/machine/spu/strcpy.h: Supply _strcpy for optimized SPU
>>> str[n]cpy and str[n]cat.
>>> * libc/machine/spu/strncat.c: Use _straddr and _strcpy.
>>> * libc/machine/spu/strncpy.c: Use _strcpy.
>>>
>>> Index: quilt/newlib/libc/machine/spu/strcat.c
>>> ===================================================================
>>> --- quilt.orig/newlib/libc/machine/spu/strcat.c
>>> +++ quilt/newlib/libc/machine/spu/strcat.c
>>> @@ -1,9 +1,6 @@
>>> /*
>>> - (C) Copyright 2001,2006,
>>> + (C) Copyright 2008
>>> International Business Machines Corporation,
>>> - Sony Computer Entertainment, Incorporated,
>>> - Toshiba Corporation,
>>> -
>>> All rights reserved.
>>> Redistribution and use in source and binary forms, with or without
>>> @@ -30,26 +27,19 @@
>>> ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
>>> POSSIBILITY OF SUCH DAMAGE.
>>> */
>>> -#include <spu_intrinsics.h>
>>> +
>>> #include <stddef.h>
>>> #include <string.h>
>>> +#include "straddr.h"
>>> +#include "strcpy.h"
>>> -/* Appends the string pointed to by src (up to and including the /0
>>> - * character) to the array pointed to by dest (overwriting the
>>> +/*
>>> + * Appends the string pointed to by src (up to and including the /0
>>> + * character) to the array pointed to by dest overwriting the
>>> * /0 character at the end of dest. The strings may not overlap and
>>> * the dest string must have enough space for the result.
>>> */
>>> -
>>> char *strcat(char * __restrict__ dest, const char * __restrict__ src)
>>> {
>>> - size_t d_len, s_len;
>>> -
>>> - /* Determine the length of the src and dest input arrays.
>>> - */
>>> - d_len = strlen(dest);
>>> - s_len = strlen(src);
>>> -
>>> - (void)memcpy((void *)(dest+d_len), (const void *)src, s_len + 1);
>>> -
>>> - return ((char *)dest);
>>> + return _strncpy(_straddr(dest), src, 0, 0, 0);
>>> }
>>> Index: quilt/newlib/libc/machine/spu/strcpy.h
>>> ===================================================================
>>> --- /dev/null
>>> +++ quilt/newlib/libc/machine/spu/strcpy.h
>>> @@ -0,0 +1,180 @@
>>> +/*
>>> + (C) Copyright 2008
>>> + International Business Machines Corporation,
>>> + All rights reserved.
>>> +
>>> + Redistribution and use in source and binary forms, with or without
>>> + modification, are permitted provided that the following conditions are met:
>>> +
>>> + * Redistributions of source code must retain the above copyright notice,
>>> + this list of conditions and the following disclaimer.
>>> + * Redistributions in binary form must reproduce the above copyright
>>> + notice, this list of conditions and the following disclaimer in the
>>> + documentation and/or other materials provided with the distribution.
>>> + * Neither the names of the copyright holders nor the names of their
>>> + contributors may be used to endorse or promote products derived from
>>> + this software without specific prior written permission.
>>> +
>>> + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
>>> + IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
>>> + TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
>>> + PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
>>> + OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
>>> + EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
>>> + PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
>>> + PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
>>> + LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
>>> + NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
>>> + SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
>>> +*/
>>> +
>>> +#include <spu_intrinsics.h>
>>> +#include "vec_literal.h"
>>> +
>>> +/*
>>> + * Supply an inline _strncpy for strcpy/cat and strncpy/cat. Relies on
>>> + * checklen and lastzero code being optimized out when they are constant
>>> + * zero values.
>>> + */
>>> +static inline void * _strncpy(char * __restrict__ dest, const char *
>>> + __restrict__ src, size_t maxlen, int
>>> + checklen, int lastzero)
>>> +{
>>> + int adjust, offset, soffset, doffset, shift;
>>> + vec_uchar16 *vsrc, *vdest;
>>> + vec_uchar16 sdata1, sdata2, sdata, shuffle;
>>> + vec_uchar16 mask1, maskzero, cmp0;
>>> + vec_uint4 nonzeroes, gathered_cmp, vtmp, vtmp2;
>>> + vec_uint4 curlen; /* assumes size_t is 4 bytes */
>>> + const vec_uint4 val31 = { 31, 31, 31, 31 };
>>> + const vec_uint4 val_0123 = { 0x00010203, 0x04050607, 0x08090A0B, 0x0C0D0E0F };
>>> + const vec_uchar16 all_ones = { 0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff,
>>> + 0xff,0xff,0xff,0xff, 0xff,0xff,0xff,0xff };
>>> +
>>> + vsrc = (vec_uchar16 *) src;
>>> + vdest = (vec_uchar16 *) dest;
>>> + soffset = (int) src & 15;
>>> + doffset = (int) dest & 15;
>>> +
>>> + if (checklen) {
>>> + /*
>>> + * Set curlen so it is the number of bytes we would copy if starting
>>> + * from vdest & ~0xf.
>>> + *
>>> + * curlen could probably be replaced by comparing vdest plus some
>>> + * offset to dest + maxlen, that would help mainly in the while loop
>>> + * but would lose only one instruction (the curlen -= 16).
>>> + */
>>> + curlen = spu_splats((unsigned int) (maxlen + doffset));
>>> + }
>>> +
>>> + /*
>>> + * Setup a shuffle pattern to align the source string with the
>>> + * alignment of the destination string.
>>> + */
>>> + vtmp = spu_cmpgt(spu_promote(doffset, 0), spu_promote(soffset, 0));
>>> + adjust = spu_extract(vtmp, 0);
>>> + offset = soffset - doffset;
>>> + offset += adjust & 16;
>>> + shuffle = spu_splats((unsigned char) offset);
>>> + shuffle = (vec_uchar16) spu_add((vec_uint4) shuffle, val_0123);
>>> +
>>> + vsrc += adjust;
>>> + sdata1 = *vsrc++;
>>> + sdata2 = *vsrc++;
>>> + sdata = spu_shuffle(sdata1, sdata2, shuffle);
>>> +
>>> + /*
>>> + * mask out leading bytes
>>> + */
>>> + mask1 = spu_rlmaskqwbyte(all_ones, -doffset);
>>> +
>>> + cmp0 = spu_and(mask1, spu_cmpeq(sdata, 0));
>>> + nonzeroes = spu_cntlz(spu_gather(cmp0));
>>> + /*
>>> + * First element of nonzeroes - 15 is the number of leading non-zero
>>> + * bytes plus 1 for the zero byte.
>>> + */
>>> + if (checklen) {
>>> + vtmp = spu_add(curlen, 15);
>>> + vtmp2 = spu_cmpgt(nonzeroes, vtmp);
>>> + nonzeroes = spu_sel(nonzeroes, vtmp, vtmp2);
>>> + }
>>> +
>>> + vtmp = spu_cmpgt(nonzeroes, val31);
>>> + /*
>>> + * Note: using immediate (constant 31) vs a vector value (val31) does
>>> + * not give different results, and we have to have a vector val31 for
>>> + * the spu_sel below, so use val31 everywhere.
>>> + */
>>> + vtmp = spu_sel(nonzeroes, val31, vtmp);
>>> + /*
>>> + * So vtmp is now min(nonzeroes, 31), the number of bytes + 16 that we
>>> + * want to copy from the first 16 bytes of the source.
>>> + */
>>> + if (checklen) {
>>> + curlen = spu_sub(vtmp, curlen);
>>> + curlen = spu_sub(15, curlen);
>>> + }
>>> +
>>> + /*
>>> + * We want a right shift 0xff with fill by ones of (vtmp - 15) bytes, but
>>> + * that doesn't exist so use spu_slqwbyte and vtmp all ones left by
>>> + * (31 - vtmp). Note: this can also use spu_rlqwbytebc with spu_rlqw.
>>> + */
>>> + shift = spu_extract(spu_sub(val31, vtmp), 0);
>>> + maskzero = spu_slqwbyte(all_ones, shift);
>>> + maskzero = spu_and(mask1, maskzero);
>>> + *vdest = spu_sel(*vdest, sdata, maskzero);
>>> +
>>> + vtmp = spu_cmpgt(nonzeroes, val31);
>>> + if (checklen) {
>>> + vtmp2 = spu_cmpgt(curlen, 0);
>>> + vtmp = spu_and(vtmp, vtmp2);
>>> + }
>>> + if (spu_extract(vtmp, 0)) {
>>> + sdata1 = sdata2;
>>> + sdata2 = *vsrc++;
>>> + sdata = spu_shuffle(sdata1, sdata2, shuffle);
>>> + cmp0 = spu_cmpeq(sdata, 0);
>>> + gathered_cmp = spu_gather(cmp0);
>>> + /*
>>> + * Copy 16 bytes at a time.
>>> + */
>>> + while ((spu_extract(gathered_cmp, 0) == 0) &&
>>> + (!checklen || (spu_extract(curlen, 0) > 15))) {
>>> + if (checklen)
>>> + curlen = spu_add(curlen, -16);
>>> + *++vdest = sdata;
>>> + sdata1 = sdata2;
>>> + sdata2 = *vsrc++;
>>> + sdata = spu_shuffle(sdata1, sdata2, shuffle);
>>> + cmp0 = spu_cmpeq(sdata, 0);
>>> + gathered_cmp = spu_gather(cmp0);
>>> + }
>>> + /*
>>> + * Copy 0 to 15 trailing bytes, either up to the smaller of curlen or
>>> + * the number of non-zero bytes.
>>> + */
>>> + nonzeroes = spu_cntlz(gathered_cmp);
>>> + if (checklen) {
>>> + vtmp = spu_add(curlen, 15);
>>> + vtmp2 = spu_cmpgt(nonzeroes, vtmp);
>>> + nonzeroes = spu_sel(nonzeroes, vtmp, vtmp2);
>>> + curlen = spu_sub(nonzeroes, curlen);
>>> + curlen = spu_sub(15, curlen);
>>> + }
>>> + shift = spu_extract(spu_sub(val31, nonzeroes), 0);
>>> + maskzero = spu_slqwbyte(all_ones, shift);
>>> + ++vdest;
>>> + *vdest = spu_sel(*vdest, sdata, maskzero);
>>> + }
>>> +
>>> + if (checklen && lastzero) {
>>> + /*
>>> + * For strncat.
>>> + */
>>> + dest[maxlen - spu_extract(curlen, 0)] = '\0';
>>> + }
>>> + return (dest);
>>> +}
>>> Index: quilt/newlib/libc/machine/spu/strcpy.c
>>> ===================================================================
>>> --- quilt.orig/newlib/libc/machine/spu/strcpy.c
>>> +++ quilt/newlib/libc/machine/spu/strcpy.c
>>> @@ -1,9 +1,6 @@
>>> /*
>>> - (C) Copyright 2001,2006,
>>> + (C) Copyright 2008
>>> International Business Machines Corporation,
>>> - Sony Computer Entertainment, Incorporated,
>>> - Toshiba Corporation,
>>> -
>>> All rights reserved.
>>> Redistribution and use in source and binary forms, with or without
>>> @@ -30,19 +27,15 @@
>>> ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
>>> POSSIBILITY OF SUCH DAMAGE.
>>> */
>>> -#include <spu_intrinsics.h>
>>> #include <stddef.h>
>>> +#include "strcpy.h"
>>> -/* Copy the string pointed to by src (up to and including the /0
>>> +/*
>>> + * Copy the string pointed to by src (up to and including the /0
>>> * character) into the array pointed to by dest. If copy between
>>> * two arrays that overlap, then behavior is undefined.
>>> */
>>> -
>>> char * strcpy(char * __restrict__ dest, const char * __restrict__ src)
>>> {
>>> - /* Due to the need to support all alignment variances, this
>>> - * function can not easily be optimized. As a result, it is
>>> - * serviced using strlen and memcpy.
>>> - */
>>> - return ((char *)memcpy((void *)dest, (const void *)src, strlen(src)+1));
>>> + return _strncpy(dest, src, 0, 0, 0);
>>> }
>>> Index: quilt/newlib/libc/machine/spu/strncat.c
>>> ===================================================================
>>> --- quilt.orig/newlib/libc/machine/spu/strncat.c
>>> +++ quilt/newlib/libc/machine/spu/strncat.c
>>> @@ -1,9 +1,6 @@
>>> /*
>>> - (C) Copyright 2001,2006,
>>> + (C) Copyright 2008
>>> International Business Machines Corporation,
>>> - Sony Computer Entertainment, Incorporated,
>>> - Toshiba Corporation,
>>> -
>>> All rights reserved.
>>> Redistribution and use in source and binary forms, with or without
>>> @@ -30,68 +27,19 @@
>>> ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
>>> POSSIBILITY OF SUCH DAMAGE.
>>> */
>>> -#include <spu_intrinsics.h>
>>> #include <stddef.h>
>>> #include <string.h>
>>> +#include "straddr.h"
>>> +#include "strcpy.h"
>>> -/* Appends the string pointed to by src (up to and including the /0
>>> +/*
>>> + * Appends the string pointed to by src (up to and including the /0
>>> * character) to the array pointed to by dest (overwriting the
>>> * /0 character at the end of dest. The strings may not overlap and
>>> * the dest string must have enough space for the result.
>>> */
>>> -
>>> -char * strncat(char * __restrict__ dest, const char * __restrict__ src, size_t n)
>>> +char * strncat(char * __restrict__ dest, const char * __restrict__ src,
>>> + size_t n)
>>> {
>>> - unsigned int cmp, skip, mask, len;
>>> - vec_uchar16 *ptr, data;
>>> - vec_uint4 cnt, gt, N;
>>> - char *dst;
>>> -
>>> - /* Determine the starting location to begin concatenation.
>>> - */
>>> - dst = dest + strlen(dest);
>>> -
>>> - /* Copy the src image until either the src string terminates
>>> - * or n characters are copied.
>>> - */
>>> - N = spu_promote((unsigned int)n, 0);
>>> -
>>> - /* Determine the string length, not including termination character,
>>> - * clamped to n characters.
>>> - */
>>> - ptr = (vec_uchar16 *)src;
>>> - skip = (unsigned int)(ptr) & 15;
>>> - mask = 0xFFFF >> skip;
>>> -
>>> - data = *ptr++;
>>> - cmp = spu_extract(spu_gather(spu_cmpeq(data, 0)), 0);
>>> - cmp &= mask;
>>> -
>>> - cnt = spu_cntlz(spu_promote(cmp, 0));
>>> - len = spu_extract(cnt, 0) - (skip + 16);
>>> -
>>> - gt = spu_cmpgt(spu_promote(len, 0), N);
>>> -
>>> - while (spu_extract(spu_andc(spu_cmpeq(cnt, 32), gt), 0)) {
>>> - data = *ptr++;
>>> - len -= 16;
>>> - cnt = spu_cntlz(spu_gather(spu_cmpeq(data, 0)));
>>> - len += spu_extract(cnt, 0);
>>> -
>>> - gt = spu_cmpgt(spu_promote(len, 0), N);
>>> - }
>>> -
>>> - /* len = MIN(len, n)
>>> - */
>>> - len = spu_extract(spu_sel(spu_promote(len, 0), N, gt), 0);
>>> -
>>> - /* Perform a memcpy of the resulting length
>>> - */
>>> - (void)memcpy((void *)dst, (const void *)src, len);
>>> -
>>> - /* Terminate the resulting concetenated string.
>>> - */
>>> - dst[len] = '\0';
>>> -
>>> - return (dest);
>>> + return _strncpy(_straddr(dest), src, n, 1, 1);
>>> }
>>> Index: quilt/newlib/libc/machine/spu/strncpy.c
>>> ===================================================================
>>> --- quilt.orig/newlib/libc/machine/spu/strncpy.c
>>> +++ quilt/newlib/libc/machine/spu/strncpy.c
>>> @@ -1,9 +1,6 @@
>>> /*
>>> - (C) Copyright 2001,2006,
>>> + (C) Copyright 2008
>>> International Business Machines Corporation,
>>> - Sony Computer Entertainment, Incorporated,
>>> - Toshiba Corporation,
>>> -
>>> All rights reserved.
>>> Redistribution and use in source and binary forms, with or without
>>> @@ -30,58 +27,16 @@
>>> ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
>>> POSSIBILITY OF SUCH DAMAGE.
>>> */
>>> -#include <spu_intrinsics.h>
>>> #include <stddef.h>
>>> #include <string.h>
>>> +#include "strcpy.h"
>>> -/* Copy the string up to n character from memory area src to
>>> - * memory area dest. The memory areas may not overlap. The
>>> - * strncpy subroutine returns a pointer to dest.
>>> +/*
>>> + * Copy the string up to n character from memory area src to memory area
>>> + * dest. The memory areas may not overlap. The strncpy subroutine returns
>>> + * a pointer to dest.
>>> */
>>> char * strncpy(char * __restrict__ dest, const char * __restrict__ src, size_t n)
>>> {
>>> - unsigned int len;
>>> - unsigned int cmp, skip, mask;
>>> - vec_uchar16 *ptr, data;
>>> - vec_uint4 cnt, gt, N;
>>> -
>>> - N = spu_promote((unsigned int)n, 0);
>>> -
>>> - /* Determine the string length, including termination character,
>>> - * clamped to n characters.
>>> - */
>>> - ptr = (vec_uchar16 *)src;
>>> - skip = (unsigned int)(ptr) & 15;
>>> - mask = 0xFFFF >> skip;
>>> -
>>> - data = *ptr++;
>>> - cmp = spu_extract(spu_gather(spu_cmpeq(data, 0)), 0);
>>> - cmp &= mask;
>>> -
>>> - cnt = spu_cntlz(spu_promote(cmp, 0));
>>> - len = spu_extract(cnt, 0) - (skip + 15);
>>> -
>>> - gt = spu_cmpgt(spu_promote(len, 0), N);
>>> -
>>> - while (spu_extract(spu_andc(spu_cmpeq(cnt, 32), gt), 0)) {
>>> - data = *ptr++;
>>> - len -= 16;
>>> - cnt = spu_cntlz(spu_gather(spu_cmpeq(data, 0)));
>>> - len += spu_extract(cnt, 0);
>>> -
>>> - gt = spu_cmpgt(spu_promote(len, 0), N);
>>> - }
>>> -
>>> - /* len = MIN(len, n)
>>> - */
>>> - len = spu_extract(spu_sel(spu_promote((unsigned int)len, 0), N, gt), 0);
>>> -
>>> - /* Padding
>>> - */
>>> - if (len != n) {
>>> - memset(dest + len, 0, n - len);
>>> - }
>>> - /* Perform a memcpy of the resulting length
>>> - */
>>> - return ((char *)memcpy((void *)dest, (const void *)src, len));
>>> + return _strncpy(dest, src, n, 1, 0);
>>> }
>>> Index: quilt/newlib/libc/machine/spu/straddr.h
>>> ===================================================================
>>> --- /dev/null
>>> +++ quilt/newlib/libc/machine/spu/straddr.h
>>> @@ -0,0 +1,75 @@
>>> +/*
>>> + (C) Copyright 2008
>>> + International Business Machines Corporation,
>>> + All rights reserved.
>>> +
>>> + Redistribution and use in source and binary forms, with or without
>>> + modification, are permitted provided that the following conditions are met:
>>> +
>>> + * Redistributions of source code must retain the above copyright notice,
>>> + this list of conditions and the following disclaimer.
>>> + * Redistributions in binary form must reproduce the above copyright
>>> + notice, this list of conditions and the following disclaimer in the
>>> + documentation and/or other materials provided with the distribution.
>>> + * Neither the names of the copyright holders nor the names of their
>>> + contributors may be used to endorse or promote products derived from
>>> + this software without specific prior written permission.
>>> +
>>> + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
>>> + IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
>>> + TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
>>> + PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
>>> + OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
>>> + EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
>>> + PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
>>> + PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
>>> + LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
>>> + NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
>>> + SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
>>> +*/
>>> +
>>> +#include <spu_intrinsics.h>
>>> +#include "vec_literal.h"
>>> +
>>> +/*
>>> + * Supply the inline _straddr for use by strncpy and strncat.
>>> +*
>>> +* _straddr: search the string s, and return the address of the first byte
>>> +* containing zero.
>>> +*/
>>> +static inline char *_straddr(const char *s)
>>> +{
>>> + unsigned int cnt, cmp, skip, mask;
>>> + vec_uchar16 *ptr, data;
>>> +
>>> + /*
>>> + * Compensate for unaligned strings.
>>> + */
>>> + ptr = (vec_uchar16 *)s; /* implicit (s & ~0xf) */
>>> + skip = (unsigned int)(ptr) & 0xf;
>>> + /*
>>> + * skip the first skip bytes starting at (s & ~0xf).
>>> + */
>>> + mask = 0xFFFF >> skip;
>>> +
>>> + data = *ptr;
>>> + cmp = spu_extract(spu_gather(spu_cmpeq(data, 0)), 0);
>>> + cmp &= mask;
>>> +
>>> + cnt = spu_extract(spu_cntlz(spu_promote(cmp, 0)), 0);
>>> +
>>> + while (cnt == 32) {
>>> + data = *++ptr;
>>> + cnt = spu_extract(spu_cntlz(spu_gather(spu_cmpeq(data, 0))), 0);
>>> + /*
>>> + * The first 16 bits for gather on a byte vector are zero, so if cnt
>>> + * is 32, none of the 16 bytes in data was zero. And, there are (cnt -
>>> + * 16) non-zero bytes in data.
>>> + */
>>> + }
>>> + /*
>>> + * The first non-zero byte is at ptr aligned down plus the number of
>>> + * non-zero bytes seen.
>>> + */
>>> + return ((char*) (((int) ptr & ~0xf) + (cnt - 16)));
>>> +}
>>>
>>>
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